# Physis

An arrow is horizontally projected from the top of a tower with an initial velocity of 15m/s.if it reaches the ground 7seconds later,calculate the height of the tower (let g=10m/s0).

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1. x[f]=at^2/2+v[i]t+x[i]
Brackets dennote a subscript.
You're given x[f], a, t,and v[i]. You can just plug in their values into the formula and solve for x[i]. The horizontal velocity is irrelevant, the height of the tower is the initial position of the arrow, and final position is gonna be when it reaches the ground,or 0.

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2. h = 0.5g*t^2.

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3. 245m

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4. S=1/2*g*t*t, h=1/2*10*7*7 h=5*49=245m

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